U.S. patent number 10,394,155 [Application Number 15/981,230] was granted by the patent office on 2019-08-27 for image forming apparatus.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Akinori Miyamoto.
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United States Patent |
10,394,155 |
Miyamoto |
August 27, 2019 |
Image forming apparatus
Abstract
An image forming apparatus includes a movable photosensitive
member, a charging roller, an electrostatic image forming portion,
a developing sleeve, a charging voltage source, a charging voltage
conducting path, a developing voltage source, a developing voltage
conducting path, and a capacitor electrically connected between an
output terminal of the charging voltage source and a ground
potential or between the charging voltage conducting path and the
ground potential. The capacitor satisfies the following
relationship: {C1/(C1+C2)}.times.Vpp.ltoreq.5 (V), where C1 (pF) is
electrostatic capacity formed by the first and second conducting
paths, C2 (pF) is electrostatic capacity of the capacitor, and Vpp
(V) is a peak-to-peak voltage of the AC component of the developing
voltage.
Inventors: |
Miyamoto; Akinori (Bando,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
64271599 |
Appl.
No.: |
15/981,230 |
Filed: |
May 16, 2018 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20180335713 A1 |
Nov 22, 2018 |
|
Foreign Application Priority Data
|
|
|
|
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May 19, 2017 [JP] |
|
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2017-100178 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G
15/0266 (20130101); G03G 15/0283 (20130101); G03G
15/065 (20130101); G03G 2215/021 (20130101); G03G
15/0907 (20130101); G03G 15/0233 (20130101) |
Current International
Class: |
G03G
15/02 (20060101); G03G 15/06 (20060101); G03G
15/09 (20060101) |
Field of
Search: |
;399/50 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
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|
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10-28328 |
|
Jan 1998 |
|
JP |
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2003-316128 |
|
Nov 2003 |
|
JP |
|
2004-184573 |
|
Jul 2004 |
|
JP |
|
2017-068081 |
|
Apr 2017 |
|
JP |
|
Primary Examiner: Lindsay, Jr.; Walter L
Attorney, Agent or Firm: Venable LLP
Claims
What is claimed is:
1. An image forming apparatus comprising: a movable photosensitive
member; a charging roller provided in contact with or proximity to
a surface of said photosensitive member and configured to
electrically discharge the surface of said photosensitive member
under application of a charging voltage consisting only of a DC
component; an electrostatic image forming portion configured to
form an electrostatic image on the charged surface of said
photosensitive member; a developing sleeve provided opposed to the
surface of said photosensitive member and configured to deposit
toner on the electrostatic image formed on the surface of said
photosensitive member under application of a developing voltage
including an AC component and a DC component; a charging voltage
source configured to output the charging voltage; a developing
voltage source configured to output the developing voltage; a first
conducting path configured to electrically connect an output
terminal of said charging voltage source to said charging roller; a
second conducting path configured to electrically connect an output
terminal of said developing voltage source to said developing
sleeve; and a capacitor electrically connected between the output
terminal of said charging voltage source and a ground potential or
between said first conducting path and the ground potential,
wherein said capacitor satisfies the following relationship:
{C1/(C1+C2)}.times.Vpp.ltoreq.5(V), where C1 (pF) is an
electrostatic capacity formed by said first and second conducting
paths, C2 (pF) is an electrostatic capacity of said capacitor, and
Vpp (V) is a peak-to-peak voltage of the AC component of the
developing voltage.
2. An image forming apparatus according to claim 1, wherein said
capacitor is electrically connected between the output terminal of
said charging voltage source and the ground potential.
3. An image forming apparatus according to claim 1, wherein said
capacitor is electrically connected between said first conducting
path and the ground potential.
4. An image forming apparatus according to claim 1, wherein the
peak-to-peak voltage Vpp is 1000 V or more and 2500 V or less.
5. An image forming apparatus according to claim 1, wherein the
electrostatic capacity C1 is 60 pF or less.
6. An image forming apparatus according to claim 1, wherein said
developing voltage source outputs the developing voltage in the
form of a DC component biased with an AC component.
7. An image forming apparatus according to claim 1, wherein said
charging voltage source and said developing voltage source are
provided on a common substrate.
8. An image forming apparatus according to claim 1, wherein the
electrostatic capacity C2 is on the order of 1000 pF.
Description
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an image forming apparatus, such
as a copying machine, a printer or a facsimile machine, using an
electrophotographic type or an electrostatic recording type.
Conventionally, for example, in order to electrically charge a
photosensitive member such as an image bearing member in the image
forming apparatus using of the electrophotographic type, as a
charging bias, a DC voltage (DC charging type) or an oscillating
voltage in the form of the DC voltage biased with an AC voltage (AC
charging type) has been applied to a charging member. In the
following, a DC component of the charging bias (including the case
where the charging bias consists only of the DC component is also
referred to as "charging DC bias" and an AC component of the
charging bias is also referred to as a "charging AC bias". Further,
in such an image forming apparatus, as a developing bias for
developing an electrostatic image formed on the photosensitive
member, an oscillating voltage in the form of a DC voltage biased
with an AC voltage has been applied to a developing member. In the
following, a DC component of the developing bias is also referred
to as a "charging DC bias" and an AC component of the developing
bias is also referred to as a "developing AC voltage".
Further, in such an image forming apparatus, the developing bias
interferes with the charging bias, so that an image defect such as
an image density fluctuation or image density non-uniformity
generates in some cases.
On the other hand, Japanese Laid-Open Patent Application
2003-316128 discloses a method in which a peak of a charging AC
bias is adjusted to a rest time of the developing AC bias in a
constitution in which a charging bias in the form of a DC voltage
biased with an AC voltage and a developing bias in the form of a DC
voltage biased with an AC voltage including a rest period are
used.
According to this conventional method, an effect of suppressing an
interference of the developing AC bias with the peak of the
charging AC bias can be expected. However, in a period other than
the rest period the interference of the developing AC bias with the
charging bias AC bias can still generate.
Particularly, in the case of the DC charging type, an output of the
charging DC bias is maintained substantially at a certain value,
and therefore, the charging DC bias cannot be outputted in
synchronism with the rest period of the developing AC bias.
Further, particularly, in the DC charging type, when the charging
DC bias fluctuates by the interference of the developing AC bias
with the charging DC bias, stripe-shaped image density
non-uniformity with respect to a longitudinal direction (direction
substantially perpendicular to a surface movement direction) of the
photosensitive member is liable to generate.
Here, in order to suppress the interference as described above, it
would be considered that a charging high-voltage transmission
circuit for connecting a charging member with a charging
high-voltage circuit and a developing high-voltage transmission
circuit for connecting a developing member with a developing
high-voltage circuit are physically spaced from each other.
However, this is one of causes of impairing downsizing of the image
forming apparatus.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided
an image forming apparatus comprising: a movable photosensitive
member; a charging roller provided in contact or proximity to a
surface of the photosensitive member and configured to electrically
discharge the surface of the photosensitive member under
application of a charging voltage consisting only of a DC
component; an electrostatic image forming portion configured to
form an electrostatic image on the charged surface of the
photosensitive member; a developing sleeve provided opposed to the
surface of the photosensitive member and configured to deposit
toner on the electrostatic image formed on the surface of the
photosensitive member under application of a developing voltage
including an AC component; a charging voltage source configured to
output the charging voltage; a first conducting path configured to
electrically connect an output terminal of the charging voltage
source to the charging roller; a developing voltage source
configured to output the developing voltage; a second conducting
path configured to electrically connect an output terminal of the
developing voltage source to the developing sleeve; and a capacitor
electrically connected between the output terminal of the charging
voltage source and a ground potential or between the first
conducting path and the ground potential, wherein the capacitor
satisfies the following relationship:
{C1/(C1+C2)}.times.Vpp.ltoreq.5 (V), where C1 (pF) is electrostatic
capacity formed by the first and second conducting paths, C2 (pF)
is electrostatic capacity of the capacitor, and Vpp (V) is a
peak-to-peak voltage of the AC component of the developing
voltage.
Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference
to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic longitudinal sectional view of an image
forming apparatus.
FIG. 2 is a schematic sectional view of a photosensitive drum and a
charging roller.
FIG. 3 is a time chart showing an operation sequence of the image
forming apparatus.
FIG. 4 is a block diagram of a voltage source substrate for
generating a charging bias and a developing bias.
FIG. 5 is a circuit block diagram of a charging and developing
substrate in Embodiment 1.
FIG. 6 is a circuit block diagram of a charging and developing
substrate in Embodiment 2.
Parts (a) and (b) of FIG. 7 are schematic views each for
illustrating a connecting position of a capacitor for suppressing
interference.
FIG. 8 is a graph showing an example of a measurement result of an
interference voltage.
FIG. 9 is a graph showing an example of a relationship between the
capacity of the capacitor for suppressing the interference and the
interference voltage.
FIG. 10 is a graph showing another example of the relationship
between the capacity of the capacitor for suppressing the
interference and the interference voltage.
Parts (a) and (b) of FIG. 11 are schematic views for illustrating a
mechanism of generation of a charging lateral stripe.
DESCRIPTION OF EMBODIMENTS
In the following, an image forming apparatus according to the
present invention will be described further specifically with
reference to the drawings.
Embodiment 1
1. General Structure and Operation of Image Forming Apparatus
FIG. 1 is a schematic longitudinal sectional view of an image
forming apparatus 10 according to this embodiment. The image
forming apparatus 10 in this embodiment is a laser beam printer in
which an image is formed by a contact charging type, a reverse
development type, and a transfer type and in which a maximum sheet
passing size is an A3 size.
The image forming apparatus 10 includes a photosensitive drum 1
which is a rotatable drum-shaped (cylindrical) electrophotographic
photosensitive member as an image bearing member. The
photosensitive drum 1 is rotationally driven in an arrow A
direction (counterclockwise direction) in the figure. At a
periphery of the photosensitive drum 1, along a rotational
direction of the photosensitive drum 1, the following means are
provided successively. First, a charging roller (roller charger) 2
which is a roller-shaped charging member (contact charging member)
as a charging means is disposed. Next, an exposure device 3 as an
exposure means (electrostatic image forming means) is disposed.
Next, a developing device 4 as a developing means is disposed.
Next, a transfer roller 5 which is a roller-shaped transfer member
(contact transfer member) as a transfer means is disposed. Next, a
cleaning device 7 as a cleaning means is disposed. Further, the
image forming apparatus 10 includes a feeding means (not shown) for
feeding a transfer(-receiving) material P to a transfer portion d
formed between the photosensitive drum 1 and the transfer roller 5,
a fixing device 6 as a fixing means provided on a downstream side
of the transfer portion d with respect to a feeding direction of
the transfer material P, and the like.
FIG. 2 is a schematic sectional view more specifically showing
constitutions of the photosensitive drum 1 and the charging roller
2. The photosensitive drum 1 is a negatively chargeable organic
photoconductor (OPC). An outer diameter of the photosensitive drum
1 is 30 mm. The photosensitive drum 1 is rotationally driven at a
process speed (peripheral speed) of 200 mm/sec in general in an
arrow R1 direction (counterclockwise) in FIG. 1 by a driving motor
(main motor) as a driving means (not shown). The photosensitive
drum 1 is constituted, as shown in FIG. 2, by applying, onto an
outer peripheral surface of an aluminum cylinder (electroconductive
drum support) 1a, three layers consisting of an undercoat layer 1b
for suppressing interference with light and for improving an
adhesive property with an upper layer, a photo-charge generating
layer 1c and a charge transporting layer 1d in this order.
The charging roller 2 is, as shown in FIG. 2, rotatably held by
shaft-supporting (bearing) members (not shown) at both end portions
of its core metal (core material) 2a with respect to a longitudinal
direction (rotational axis direction). The charging roller 2 is
urged toward a center direction of the photosensitive drum 1 by an
urging spring 2e as an urging means at both end portions thereof.
As a result, the charging roller 2 is press-contacted to the
surface of the photosensitive drum 1 with a predetermined urging
force, and is rotationally driven in an arrow R2 direction
(clockwise direction) in the figure by rotation of the
photosensitive drum 1. A press-contact portion between the
photosensitive drum 1 and the charging roller 2 is a charging nip
a.
The charging process of the surface of the photosensitive drum 1 as
a portion-to-be-charged is made by the electric discharge
generating between the charging roller 2 and the photosensitive
drum 1. For that reason, the charging of the photosensitive drum 1
is started by applying a voltage of a certain threshold voltage or
more to the charging roller 2. In this embodiment, when a negative
DC voltage of about 600 V or more as an absolute value is applied
to the charging roller 2, an absolute value of a surface potential
of the photosensitive drum 1 starts to increase, and thereafter
linearly increases with a slope of substantially 1 relative to an
applied voltage. For example, in order to obtain the surface
potential of -300 V, the DC voltage of -900 V may only be required
to be applied, and in order to obtain the surface potential of -500
V, the DC voltage of -1100 V may only be required to be applied to
the charging roller 2. This threshold voltage is defined as a
discharge start voltage (charge start voltage) Vth. That is, in
order to obtain the dark portion potential VD which is the surface
potential of the photosensitive drum 1 required for the
electrophotographic process, to the charging roller 2, there is a
need to apply a direct-current voltage (DC voltage) of not less
than the above-described dark portion potential VD, such as
VD+Vth.
To the core metal 2a of the charging roller 2, from a charging
voltage source S1 (corresponding to a charging high-voltage circuit
300 described later) as a charging bias applying means, a charging
bias (charging voltage, charging high-voltage) is applied under a
predetermined condition. As a result, the peripheral surface the
photosensitive drum 1 is electrically charged to a predetermined
polarity (negative in this embodiment) and a predetermined
potential. In this embodiment, during image formation, in order
that the peripheral surface of the photosensitive drum 1 is
substantially uniformly charged to the dark portion potential
VD=-500 V, as the charging bias, the DC voltage of -1100 V is
applied from the charging voltage source S1 to the charging roller
2 (DC charging type).
The charging roller 2 has a length of 320 mm with respect to its
longitudinal direction. As shown in FIG. 2, the charging roller 2
has, on an outer peripheral surface of the core metal (supporting
member) 2a, three layers consisting of a lower layer 2b, an
intermediary layer 2c, and a surface layer 2d successively
laminated from below. The lower layer 2b is a foam sponge layer for
decreasing charging noise. The surface layer 2d is a protective
layer provided for preventing an occurrence of leakage even when a
pin hole generates on the photosensitive drum 1. More specifically,
the charging roller 2 in this embodiment has the following
specification.
Core metal 2a: stainless steel rod with a diameter of 6 mm
Lower layer 2b: carbon-dispersed foam EPDM (specific gravity: 0.5
g/cm.sup.3, volume resistivity: 10.sup.2-10.sup.9 ohm.cm, layer
thickness: 3.0 mm)
Intermediary layer 2c: carbon-dispersed NBR rubber (volume
resistivity: 10.sup.2-10.sup.5 ohm.cm, layer thickness: 700
.mu.m)
Surface layer 2d: fluorinated "Torejin" resin in which tin oxide
and carbon particles are disposed (volume resistivity:
10.sup.7-10.sup.10 ohm.cm, surface roughness (JIS ten-point average
surface roughness Ra): 1.5 .mu.m, layer thickness: 10 .mu.m)
The exposure device 3 is a laser beam scanner including a
semiconductor laser. The exposure device 3 outputs laser light
(beam) L modulated correspondingly to an image signal inputted from
an image reading device (not shown). The exposure device 3 subjects
the substantially uniformly charged surface of the photosensitive
drum 1 to scanning exposure (image exposure) to the light L at an
exposure portion b. By this, an absolute value of the potential of
the surface of the photosensitive drum 1 at a portion which has
been irradiated with the laser light L lowers, so that an
electrostatic latent image (electrostatic image) corresponding to
the image information is formed on the surface of the
photosensitive drum 1. For example, the dark portion potential VD
of the photosensitive drum 1 is -500 V, and the light portion
potential VL which is the surface potential at an exposed portion
of the photosensitive drum 1 is -150 V. In this embodiment, a
maximum light quantity of the exposure means 3 is 8 mW.
The developing device 4 is of a two-component magnetic brush
developing type. The developing device 4 deposits the toner charged
to a charge polarity (negative in this embodiment) of the
photosensitive drum 1 on the exposed portion (light portion) of the
surface of the photosensitive drum 1 and reversely develops the
electrostatic latent image, so that the toner image is formed on
the surface of the photosensitive drum 1. The developing device 4
includes a developing container 4a in which a two-component
developer 4e which is a mixture of principally non-magnetic toner
particles (toner) and magnetic carrier particles (carrier) is
accommodated as the developer. At an opening of the developing
container 4a provided at an opposing portion to the photosensitive
drum 1, a developing sleeve 4b, as a developer carrying member,
incorporating a fixed magnet roller 4c as a magnetic field
generating means and being constituted by a non-magnetic material
is rotatably provided. The developer 4e accommodated in the
developing container 4a is constrained on the developing sleeve 4b
by a magnetic force of the magnet roller 4c and is coated on the
developing sleeve 4b in a thin layer. Then, the developer 4e is fed
by rotation of the developing sleeve 4b to a developing portion c
where the photosensitive drum 1 and the developing sleeve 4b oppose
each other. The developer 4e in the developing container 4a is fed
toward the developing sleeve 4b while being stirred substantially
uniformly by rotation of two developer-stirring members 4f.
In this embodiment, the carrier has a volume resistivity of about
10.sup.13 ohmcm and an average particle size of 40 .mu.m, and the
toner is triboelectrically charged to a negative polarity by
friction with the carrier. The toner content (concentration) of the
developer 4e in the toner container 4a is detected by a
concentration (density) sensor (not shown). On the basis of this
detected information, the toner is supplied in an appropriate
amount from a toner hopper 4g to the developing container 4a, so
that the toner content of the developer 4e in the developing
container 4a is adjusted to a substantially constant level. At the
developing portion c, the closest distance of the developing sleeve
4b to the photosensitive drum 1 is kept at 300 and the developing
sleeve 4b is disposed opposed to the photosensitive drum 1. The
developing sleeve 4b is rotationally driven in a direction
(counterclockwise) indicated by an arrow R4 in FIG. 1 so that
surface movement directions of the photosensitive drum 1 and the
developing sleeve 4b are opposite devices at the developing portion
c. To the developing sleeve 4b, a developing bias (developing
voltage, developing high-voltage) is applied from a developing
voltage source S2 (corresponding to a developing high-voltage
circuit 400 described later) as a developing bias applying means
under a predetermined condition. In this embodiment, as the
developing bias, an oscillating voltage in the form of a DC voltage
(Vdc) biased with an AC voltage (Vac) is applied from the
developing voltage source S2 to the developing sleeve 4b. More
specifically, in this embodiment, as the developing bias, the
oscillating voltage in the form of the DC voltage (-320 V) biased
with the AC voltage having a frequency of 8 kHz and a peak-to-peak
voltage of 1800 Vpp is applied to the developing sleeve 4b.
The transfer roller 5 is contacted to the photosensitive drum 1
with a predetermined urging force, and a transfer portion d is
formed at a contact portion between the photosensitive drum 1 and
the transfer roller 5. The transfer roller 5 is rotated in an arrow
R5 direction (clockwise direction) in the figure by rotation of the
photosensitive drum 1. To the transfer roller 5, from a transfer
voltage source S3 as a transfer bias applying means, a transfer
bias (transfer voltage, transfer high-voltage) is applied under a
predetermined condition. In this embodiment, as a transfer bias
which is a DC voltage of +500 V of an opposite polarity (positive
in this embodiment) to the charge polarity (normal charge polarity)
of the toner during development is applied from the transfer
voltage source S3 to the transfer roller 5. The toner image on the
photosensitive drum 1 is transferred onto the transfer material P
such as a recording sheet (paper) at the transfer portion d.
The fixing device 6 includes a rotatable fixing roller 6a and a
rotatable pressing roller 6b. The fixing device 6 fixes the toner
image on the transfer material P under heat and pressure
application while sandwiching and feeding the transfer material P
at a fixing nip between the fixing roller 6a and the pressing
roller 6b. Rotatable speeds of the fixing roller 6a and the
pressing roller 6b are changeable depending on a material, a
thickness and a basis weight of the transfer material P.
The cleaning device 7 removes and collects the toner (transfer
residual toner), remaining on the surface of the photosensitive
drum 1 after the transfer of the toner image onto the transfer
material P, from the surface of the photosensitive drum 1. The
cleaning device 7 rubs the surface of the rotating photosensitive
drum 1 with a cleaning blade 7a contacting the photosensitive drum
1. By this, the surface of the photosensitive drum 1 is cleaned by
being subjected to removal of the transfer residual toner, and is
repetitively subjected to the image formation. A contact portion
between the cleaning blade 7a and the surface of the photosensitive
drum 1 is a cleaning portion e.
FIG. 3 is a chart showing an operation sequence of the image
forming apparatus 10 in this embodiment.
a. Initial Rotation Operation (Pre-Multi-Rotation Step)
An initial rotation operation (pre-multi-rotation step) is
performed in a period in which a starting operation (actuation
operation, warming operation) during actuation of the image forming
apparatus 10 is performed. The rotational drive of the
photosensitive drum 1 is started by turning on a power source
switch of the image forming apparatus 10, and a preparatory
operation of a predetermined process device, such as rising of the
fixing device 6 to a predetermined temperature, is executed.
b. Print-Preparatory Rotation Operation (Pre-Rotation Step)
The print-preparatory rotation operation (pre-rotation step) is
performed in a period from turning-on of a print signal (an image
formation start signal) until an image forming step (printing step)
is actually started, in which the preparatory operation before the
image formation is performed. When the print signal is inputted
during the initial rotation operation, the operation is executed
subsequently to the initial rotation operation. When there is no
input of the print signal during the initial rotation operation,
the drive of a main motor is once stopped after the end of the
initial rotation operation and the rotational drive of the
photosensitive drum 1 is stopped, so that the image forming
apparatus 10 is maintained in a stand-by state (stand-by) until a
(subsequent) print signal is inputted. Then, when the print signal
is inputted, the print-preparatory rotation operation is
executed.
c. Printing Step (Image Forming Step)
The printing step (image forming step) is performed in a period in
which formation, transfer and fixing of the toner image are carried
out. When a predetermined print-preparatory rotation operation is
ended, subsequently an image forming process on the photosensitive
drum 1 is executed, so that the transfer of the toner image formed
on the surface of the photosensitive drum 1 onto the transfer
material P, the fixing process of the toner image by the fixing
device 6, and the like are made and thus an image-formed product is
printed out. In the case of an operation in a continuous printing
(continuous print) mode, the above-described printing step is
repetitively executed correspondingly to a predetermined set print
number n.
d. Sheet-Interval Step
A sheet-interval step is performed in a period corresponding to a
non-passing state of the transfer material P through a transfer
position d, from after passing of a trailing end of a transfer
material P through the transfer position d until a leading end of a
subsequent transfer material P reaches the transfer position d.
e. Post-Rotation Operation
A post-rotation step is performed in a period in which the
photosensitive drum 1 is rotationally driven by continuing the
drive of the main motor for some time even after the printing step
for a final transfer material P is ended, and thus a predetermined
post-operation is executed. In this embodiment, during this
post-rotation operation, correspondingly to one full circumference
of the photosensitive drum 1, the photosensitive drum 1 is
irradiated with the light by the exposure device 3, so that a step
of discharging (removing) residual electric charges on the
photosensitive drum 1 is performed.
f. Stand-by Step
When the predetermined post-operation is ended, the drive of the
main motor is stopped and thus the rotational drive of the
photosensitive drum 1 is stopped, so that the image forming
apparatus 10 is maintained in a stand-by state until a subsequent
print signal is inputted. In the case of printing of a single
sheet, after the end of the printing, the image forming apparatus
10 is in the stand-by state through the post-rotation operation. In
the stand-by state, when the print signal is inputted, the
operation of the image forming apparatus 10 shifts to the
print-preparatory rotation operation.
During the printing step c described above is during the image
formation, whereas during the initial rotation operation a, during
the print-preparatory operation b, during the sheet-interval step d
and during the post-rotation operation e, which are described
above, are during non-image formation.
In the above, the general structure and operation of the image
forming apparatus were described taking, as an example, the case
where the image forming apparatus includes a single photosensitive
drum. However, the present invention is equivalently applicable to
a tandem-type image forming apparatus including a plurality of
photosensitive drums. As such an image forming apparatus, a tandem
image forming apparatus employing an intermediary transfer type
including an intermediary transfer member and a tandem image
forming apparatus employing a direct transfer type including a
transfer material carrying member are well known. In the tandem
image forming apparatus employing the intermediary transfer type,
for example, toner images formed on a plurality of photosensitive
drums are primary-transferred superposedly onto an intermediary
transfer belt formed with an endless surface as an intermediary
transfer member and thereafter are secondary-transferred onto the
transfer material. This image forming apparatus includes, for
example, a plurality of image forming portions each including a
photosensitive drum 1, a charging roller 2, an exposure device 3, a
developing device 4, a transfer roller (primary transfer roller) 5
and a cleaning device 7 which are similar to those of the image
forming apparatus 10 shown in FIG. 1. In the tandem image forming
apparatus employing the direct transfer type, for example, toner
images formed on a plurality of photosensitive drums are
transferred superposedly onto a transfer material carried and fed
by a transfer belt formed with an endless belt as a transfer
material carrying member. This image forming apparatus includes,
for example, a plurality of image forming portions each including a
photosensitive drum 1, a charging roller 2, an exposure device 3, a
developing device 4, a transfer roller 5 and a cleaning device 7
which are similar to those of the image forming apparatus 10 shown
in FIG. 1.
2. Structure of High-Voltage Source
Next, a structure of a high-voltage source for outputting the
charging bias and the developing bias in this embodiment will be
described. In this embodiment, as described above, the image
forming apparatus 10 includes the plurality of image forming
portions each provided with a charging high-voltage circuit 300 and
a developing high-voltage circuit 400. The plurality of image
forming portions form toner images of yellow (Y), magenta (M), cyan
(C) and black (K), respectively, and in the case where elements for
these colors are distinguished from each other, Y, M, C and K are
added to ends of reference numerals (symbols) thereof.
FIG. 4 is a block diagram showing the structure of the high-voltage
source for outputting the charging bias and the developing bias.
The image forming apparatus 10 includes charging and developing
substrates 200Y, 200M, 200C and 200K which are high-voltage
substrates (composite high-voltage source substrate) and includes a
control substrate 100.
The charging and developing substrate 200Y for the yellow is a
high-voltage source including a charging high-voltage circuit 300Y
for generating output of a voltage (charging high voltage) applied
to the charging roller 2Y and a developing high-voltage circuit
400Y for generating output of a voltage (developing high voltage)
applied to a developing sleeve 4bY. The charging and developing
substrate 200M for the magenta is a high-voltage source including a
charging high-voltage circuit 300M for generating output of a
voltage (charging high voltage) applied to the charging roller 2M
and a developing high-voltage circuit 400M for generating output of
a voltage (developing high voltage) applied to a developing sleeve
4bM. The charging and developing substrate 200C for the cyan is a
high-voltage source including a charging high-voltage circuit 300C
for generating output of a voltage (charging high voltage) applied
to the charging roller 2C and a developing high-voltage circuit
400C for generating output of a voltage (developing high voltage)
applied to a developing sleeve 4bC. The charging and developing
substrate 200K for the black is a high-voltage source including a
charging high-voltage circuit 300K for generating output of a
voltage (charging high voltage) applied to the charging roller 2K
and a developing high-voltage circuit 400K for generating output of
a voltage (developing high voltage) applied to a developing sleeve
4bK.
The control substrate 100 carries out a start of an operation and
output voltage setting of each of the charging and developing
substrates 200Y, 200M, 200C and 200K for an associated image
forming portion and carries out acquisition of a detection value in
each of the charging and developing substrates 200Y, 200M, 200C and
200K for the associated image forming portion. In this embodiment,
the control substrate 100 carries out control of a general
operation of the image forming apparatus 10.
Here, the charging and developing substrates 200Y, 200M, 200C and
200K for the respective image forming portions have substantially
the same structure. Accordingly, in the following, description will
be made by paying attention to one charging and developing
substrate as a representative, and suffixes Y, M, C and K of the
reference numerals or symbols for representing elements for the
respective colors will be omitted.
3. Charging Developing Substrate
FIG. 5 is a circuit block diagram of the charging and developing
substrate 200. The charging and developing substrate 200 includes
the charging high-voltage circuit 300 for generating the charging
high voltage and the developing high-voltage circuit 400 for
generating the developing high voltage. The developing high-voltage
circuit 400 includes a developing DC high voltage circuit 600 for
generating output of a DC voltage and a developing AC high voltage
circuit 500 for generating output of an AC voltage.
The charging high-voltage circuit 300 includes a charging output
control circuit 301, a charging transformer driving circuit 302, a
charging rectifying and smoothing circuit 303, a charging voltage
detecting circuit 304, a charging current detecting circuit 305 and
a charging over current protecting circuit 306 and the like. The
charging output control circuit 301 is a circuit for outputting a
voltage so that a charging output set voltage set by a CPU 101 of
the control substrate 100 coincides with a value outputted from the
charging voltage detecting circuit 304 described later. The
charging transformer driving circuit 302 is a circuit for driving a
transformer 307 on the basis of a charging transformer driving
clock inputted from the CPU 101 of the control substrate 100. The
charging rectifying and smoothing circuit 303 is a circuit for
outputting a DC voltage by rectifying and smoothing output of an AC
voltage from the transformer 307. The charging voltage detecting
circuit 304 is a circuit for converting a charging high voltage
into a voltage with a low voltage level and outputting the
converted voltage. The charging current detecting circuit 305 is a
circuit for converting a current (charging current) flowing from
the charging high-voltage circuit 300 to the charging roller 2 into
a voltage and outputting the converted voltage. An output (charging
current detection value) of the charging current detecting circuit
305 is used for the purposes of input of the output to the charging
over current protecting circuit 306 and of detection of charging
abnormality of the photosensitive drum 1. The charging over current
protecting circuit 306 is a circuit for stopping application of the
charging high voltage by stopping the charging transformer driving
circuit 302 when the charging current detecting value exceeds a
predetermined value and is a circuit for protecting the apparatus
so that the output is prevented from excessively increasing during
substrate failure.
The charging DC bias outputted from the charging high-voltage
circuit 300 is applied to the charging roller 2 via a charging
high-voltage transmission circuit (wiring) 800 for connecting the
charging high-voltage circuit 300 with the charging roller 2.
The developing DC high voltage circuit 600 includes a developing DC
output control circuit 601, a developing DC transformer driving
circuit 602, a developing DC rectifying and smoothing circuit 603,
a developing DC voltage detecting circuit 604 and the like. The
developing DC output control circuit 601 is a circuit for
outputting a voltage so that a developing DC output set voltage set
by a CPU 101 of the control substrate 100 coincides with a value
outputted from the developing DC voltage detecting circuit 604
described later. The developing DC transformer driving circuit 602
is a circuit for driving a transformer 605 on the basis of a
developing DC transformer driving clock inputted from the CPU 101
of the control substrate 100. The developing DC rectifying and
smoothing circuit 603 is a circuit for outputting a DC voltage by
rectifying and smoothing output of an AC voltage from the
transformer 605. The developing DC voltage detecting circuit 604 is
a circuit for converting a developing high voltage into a voltage
with a low voltage level and outputting the converted voltage.
The developing AC high voltage circuit 500 includes a developing AC
output control circuit 501, a developing AC transformer driving
circuit 502, a developing AC current detecting circuit 503 and a
developing AC over current protecting circuit 504 and the like. The
developing AC output control circuit 501 is a circuit for
outputting a predetermined voltage by setting of a developing AC
output set voltage by a CPU 101 of the control substrate 100. The
developing AC transformer driving circuit 502 is a full-bridge
circuit for driving a transformer 505 on the basis of a developing
AC transformer driving clock inputted from the CPU 101 of the
control substrate 100. The charging current detecting circuit 503
is a circuit for converting an AC current (developing AC current)
flowing to the developing sleeve 4b into a voltage and outputting
the converted voltage. An output (developing AC current detection
value) of the developing AC current detecting circuit 503 is used
for the purposes of input of the output to the developing AC over
current protecting circuit 504 and of detection of abnormality of
high-voltage application to the developing sleeve 4b. The
developing AC over current protecting circuit 504 is a circuit for
stopping application of the developing AC high voltage by stopping
the developing AC transformer driving circuit 502 when the charging
current detecting value exceeds a predetermined value and is a
circuit for protecting the apparatus so that the output is
prevented from excessively increasing during substrate failure.
The developing bias in the form of the developing DC bias
superposed with the developing AC bias, which biases are outputted
from the developing high-voltage circuit 400, is applied to the
developing sleeve 4b via a developing high-voltage transmission
circuit (wiring) 900 for connecting the developing high-voltage
circuit 400 with the developing sleeve 4b.
Further, in this embodiment, the charging high-voltage circuit 300
is provided with a diode OR circuit 700. The diode OR circuit 700
is constituted by including two diodes. An anode side of each of
the diodes is connected with lines of a charging current detection
value and a developing AC current charging roller detection value,
and cathode sides of the respective diodes are connected with each
other ("diode OR"). The diode OR circuit 700 is a circuit for
outputting signals of the respective diodes as a single signal
(high voltage current detection signal, herein also referred to as
"IS"). By using the diode OR circuit 700, IS, which is a higher
value of the charging current detection value and the developing AC
current detection value, is outputted. That is, IS represents the
developing AC current detection value when the developing AC
current detection value is higher than the charging current
detection value, and represents the charging current detection
value when the charging current detection value is higher than the
developing AC current detection value. In actuality, a value
obtained by subtracting an amount corresponding to a forward
direction drop voltage (about 0.6 V) of the diode from each of the
detection values is IS. In the case where the charging current
detecting circuit 305 and the developing AC current detecting
circuit 503 are directly connected with each other and not through
the diode OR circuit 700, the current flows from the charging
current detecting circuit 305 to the developing AC current
detecting circuit 503 or flows in an opposite direction thereof, so
that a correct value cannot be detected. For that reason, in this
embodiment, by using the diode OR circuit 700, flowing-in of the
current between the detection circuits is prevented by the
diodes.
4. Charging Lateral Stripe
As described above, particularly in the DC charging type, when the
developing AC bias interferes with the charging DC bias and thus
the charging DC bias fluctuates, stripe-shaped image density
non-uniformity in the longitudinal direction (substantially
perpendicular to a surface movement direction) of the
photosensitive member (photosensitive drum) is liable to generate.
Here, the stripe-shaped image density non-uniformity is referred to
as a "charging lateral stripe". Further, a minute gap between the
photosensitive member and the charging member is referred to as a
"charging gap". Of the charging gap, a portion thereof on a side
upstream of the closest portion between the photosensitive member
and the charging member (in the case where the photosensitive
member and the charging member contact each other, this portion is
a contact portion) with respect to the movement direction of the
surface (to be electrically charged) of the photosensitive member
is referred to as an "upstream gap". Further, of the charging gap,
a portion thereof on a side downstream of the closest portion
(contact portion) between the photosensitive member and the
charging member with respect to the surface movement direction of
the photosensitive member is referred to as a "downstream gap".
FIG. 11 is a schematic view for illustrating a mechanism of
generation of the charging lateral stripe in the constitution of
this embodiment. The photosensitive drum 1 and the charging roller
2 are disposed in contact with each other. The photosensitive drum
1 and the charging roller 2 rotate so that their surface movement
directions are the same at the contact portion (charging nip) a. At
this time, in an upstream gap A1, a potential difference between
the photosensitive drum 1 and the charging roller 2 exceeds a
discharge start threshold based on Paschen's law and thus electric
discharge generates, so that electric charges are placed on the
photosensitive drum 1 and thus a surface potential of the
photosensitive drum 1 is a predetermined dark portion potential
(VD). When the electric discharge normally generates in the
upstream gap A1, as shown in part (a) of FIG. 11, uniform charging
of the photosensitive drum 1 is completed, so that an image defect
such as the charging lateral stripe does not generate.
However, when the developing AC bias interferes with the charging
DC bias, a desired charging DC circuit is not applied to the
charging roller 2, so that the uniform charging of the
photosensitive drum 1 is not completed in the upstream gap A1 in
some instances. In the case where the uniform charging of the
photosensitive drum 1 is not completed in the upstream gap A1, as
shown in (b) of FIG. 11, incomplete (non-uniformity) minute
discharge generates in a downstream gap A2, and at a portion
thereof, the surface potential of the photosensitive drum 1 causes
non-uniformity thereof, so that the charging lateral stripe
generates.
5. Capacitor for Suppressing Interference
In this embodiment, as shown in FIG. 5, in order to suppress the
image defect such as the charging lateral stripe as described
above, in the charging high-voltage circuit 300, a capacitor 50 for
suppressing the interference of the developing AC bias with the
charging DC bias is provided.
As regards the interference of the developing AC bias with the
charging DC bias, leakage due to capacitive coupling resulting from
line capacity generating between the charging high-voltage
transmission circuit 800 and the developing high-voltage
transmission circuit 900 is one of causes of the interference. In
this embodiment, the line capacity generating between the charging
high-voltage transmission circuit 800 and the developing
high-voltage transmission circuit 900, i.e., line capacity
generating between connecting lines (wires) for supplying biases to
the charging roller 2 and the developing sleeve 4b, is also
referred simply to as "line capacity". Particularly, as in this
embodiment, in the case where the charging high-voltage circuit 300
and the developing high-voltage circuit 400 are provided on a
common substrate (composite high voltage source substrate), a
physical distance between the charging high-voltage transmission
circuit 800 and the developing high-voltage transmission circuit
900 becomes relatively short (close), and therefore, this
interference is liable to generate.
For that reason, the capacitor 50 is required to be connected with
a portion where the line capacity generates. In this embodiment,
the capacitor 50 is provided between an output terminal of the
charging high-voltage circuit 300 and GRD (ground earth, ground) in
the high voltage substrate (charging and developing substrate) 200.
Specifically, in this embodiment, as schematically shown in part
(a) of FIG. 7, an output terminal 60 of the charging high-voltage
circuit 300 is provided with a protective resistor 70 for
countermeasure against over current. Further, one of terminals of
the capacitor 50 is connected in series with a wiring lead of a
subsequent stage (charging roller 2 side) to the protective
resistor 70 in the charging high-voltage circuit 300, and the other
terminal is connected with the GRD in the high voltage substrate
(charging and developing substrate) 200. That is, in this
embodiment, a connecting position of the capacitor 50 is between
the output terminal of the charging high-voltage circuit 300 and
the GRD, and is connected in series with the connecting position
between the output terminal of the charging high-voltage circuit
300 and the GRD.
A magnitude of an interference voltage of the developing AC bias
with the charging DC bias is roughly determined by a peak-to-peak
voltage of the developing AC bias and a divided voltage between the
line capacity and capacity of the capacitor 50. Here, the line
capacity is "C1", the capacity of the capacitor 50 is "C2", and the
peak-to-peak voltage of the developing AC bias is "Vpp". At this
time, the magnitude of the interference voltage of the developing
AC bias with the charging DC bias can be made sufficiently small by
making the capacity C2 of the capacitor 50 sufficiently larger than
the line capacity C1 under predetermined developing bias setting
(Vpp, frequency). As a result, the image defect such as the
charging lateral stripe can be sufficiently suppressed.
The capacity C2 of the capacitor 50 can be set depending on the
line capacity C1 and the constitution of the image forming
apparatus 10 including the developing bias setting, so that the
interference voltage of the developing AC bias with the charging DC
bias can be sufficiently reduced. In this embodiment, as
specifically described later, the capacity C2 of the capacitor 50
is set depending on the line capacity C1 so as to satisfy the
following formula: {C1/(C1+C2)}.times.Vpp(V).ltoreq.5(V).
In the formula, the left side represents an amount of a fluctuation
of the potential of the charging high-voltage transmission circuit
800 when the potential of the developing high-voltage transmission
circuit 900 fluctuates only by Vpp, i.e., the magnitude of the
interference voltage of the developing AC bias with the charging DC
bias. That is, depending on the line capacity C1, the capacity C2
of the capacitor C1 may preferably be set so that the interference
voltage of the developing AC bias with the charging DC bias is not
more than 5 (V) as shown in the right side of the above-described
formula. As a result, the image defect such as the charging lateral
stripe can be sufficiently suppressed without increasing the
capacity C2 of the capacitor 50 more than necessary.
Incidentally, in this embodiment, the line capacity C1 is 20 (pF),
and the peak-to-peak voltage Vpp of the developing AC bias is 1750
(V). For that reason, the capacity C2 of the capacitor 50 was set
at 9400 (pF). As a result, in the above-described formula, the left
side is 3.7 (V), and therefore the above-described formula holds,
so that it is possible to sufficiently suppress the image defect
such as the charging lateral stripe.
Here, the line capacity C1 between the charging high-voltage
transmission circuit 800 and the developing high-voltage
transmission circuit 900 is calculated by the following formula
through measurement of a fluctuation V of the charging DC bias
(voltage value) of a current flowing through the charging
high-voltage transmission circuit 800 by using an oscilloscope
manufactured by Tektronix Inc. C1=C2.times.V/(Vpp-V)
Further, the capacity C2 of the capacitor 50 was a value measured
using an LCR meter manufactured by HIOKI E.E. Corp.
FIG. 8 shows an example of a result of measurement of the
fluctuation amount of the charging DC bias (voltage value) in the
case where the capacitor 50 is not provided in the constitution of
this embodiment. As shown in FIG. 8, in the case where the
capacitor 50 is not provided, a waveform of the charging DC bias
shows an amplitude due to the influence of the developing AC bias.
An average of peaks when the charging DC bias fluctuates so that an
absolute value of the charging DC bias becomes large is a maximum
(value), and an average of peaks when the charging DC bias
fluctuates so that the absolute value becomes small is a minimum
(value). At this time, a difference between the maximum and the
minimum is an interference voltage .DELTA.V of the developing AC
bias with the charging DC bias. In the case of an example of FIG.
8, the interference voltage .DELTA.V is about 10 (V).
FIG. 9 shows a result of measurement of a change in interference
voltage .DELTA.V when the capacity C2 of the capacitor 50 was
changed in the constitution of this embodiment. From FIG. 9, it is
understood that the interference voltage .DELTA.V gradually
decreases with an increasing capacity C2 of the capacitor 50.
Table 1 appearing hereinafter shows a result of a check on a degree
of generation of the charging lateral stripe due to the
interference voltage .DELTA.V. The charging lateral stripe was
evaluated by checking whether or not a stripe-shaped image in a
direction perpendicular to the feeding direction (i.e., in a
direction substantially parallel to a rotational axis direction of
the photosensitive drum 1) is generated on a half-tone image
through eye observation. The lateral stripe image was evaluated as
"x (poor)" in the case where the lateral stripe image generated to
an unacceptable degree, and was evaluated as "o (good)" in the case
where the lateral stripe image did not generate.
TABLE-US-00001 TABLE 1 IV*.sup.1 (V) 34.3 17.3 11.5 7.4 6.9 3.7
LSI*.sup.2 x x x x x .smallcircle. *.sup.1"IV" is the interference
voltage (V). *.sup.2"LSI" is the lateral stripe image.
As shown in Table 1, in the case where the interference voltage
.DELTA.V was 3.7 (V) (in this embodiment), the charging lateral
stripe (lateral stripe image) did not generate. On the other hand,
in the cases of the interference voltages of not less than 6.9 (V),
the charging lateral stripe generated. As a result of further
study, it turned out that when the interference voltage .DELTA.V
was not more than 5 (V), the charging lateral stripe did not
generate or was able to be alleviated to the acceptable degree.
As a result of study made similarly as the above-described study,
it turned out that a good result was able to be obtained by making
the interference voltage .DELTA.V not more than 5 (V) in a range
such that the peak-to-peak voltage Vpp of the developing AC bias is
1000 (V) or more and 2500 (V) or less. Further, as a result of
study made similarly as the above-described study, even when the
interference C1 is large to a degree of about 60 (pF) or less,
which is possible in the case where the composite high voltage
source substrate is used as in this embodiment, a good result was
able to be obtained by making the interference voltage .DELTA.V not
more than 5 (V). Incidentally, in the case where the composite high
voltage source substrate is used as in this embodiment, typically,
the line capacity is 5 (pF) or more. FIG. 10 shows several examples
a relationship between the capacity C2 of the capacitor 50 and the
interference voltage .DELTA.V and a check result of the degree of
generation of the charging lateral stripe in other constitution
examples. Incidentally, in a constitution 1 ("CNS. 1") in FIG. 10,
the line capacity C1 is 14 (pF), and the peak-to-peak voltage Vpp
of the developing AC bias is 1500 (V). Further, in a constitution 2
("CNS. 2"), the line capacity C1 is 8 (pF), and the peak-to-peak
voltage Vpp of the developing AC bias is 1600 (V). Further, in a
constitution 3 ("CNS. 3"), the line capacity C1 is 6.5 (pF), and
the peak-to-peak voltage Vpp of the developing AC bias is 1750
(V).
As described above, in this embodiment, depending on the line
capacity between the charging high-voltage transmission circuit 800
and the developing high-voltage transmission circuit 900, the
capacitor 50 for suppressing the interference of the developing AC
bias with the charging DC bias is provided in the charging and
developing substrate. As a result, the interference between the
charging bias and the developing bias which are outputted from the
composite high voltage source substrate is sufficiently suppressed,
so that the image defect such as the charging lateral stripe can be
sufficiently suppressed. Accordingly, according to the present
invention, it is possible to suppress the image defect due to the
interference between the charging bias and the developing bias
while downsizing the image forming apparatus.
Embodiment 2
Next, another embodiment of the present invention will be
described. Basic constitution and operation of an image forming
apparatus in this embodiment are the same as those in Embodiment 1.
Accordingly, elements having the same or corresponding functions or
constitutions as those of the image forming apparatus in Embodiment
1 are represented by the same reference numerals or symbols, and
will be omitted from detailed description.
FIG. 6 is a circuit block diagram of a charging and developing
substrate 200 in this embodiment. In this embodiment, a capacitor
50 for suppressing the interference of the developing AC bias with
the charging DC bias is provided in the charging high-voltage
transmission circuit 800.
As described in Embodiment 1, the capacitor 50 is required to be
connected with a portion where the line capacity generates. For
that reason, in this embodiment, the capacitor 50 is provided
between GRD (ground earth, ground) and a connecting line (wiring
lead) between the charging high-voltage circuit 300 and the
charging roller 2. Specifically, in this embodiment, as
schematically shown in part (b) of FIG. 7, one of terminals of the
capacitor 50 is connected in series with a wiring lead of the
charging high-voltage transmission circuit 800, and the other
terminal is connected with the GRD. That is, in this embodiment, a
connecting position of the capacitor 50 is between the charging
high-voltage transmission circuit 800 and the GRD, and is connected
in series with the connecting position between the charging
high-voltage transmission circuit 800 and the GRD.
Incidentally, also in the constitution of this embodiment, the
capacity C2 of the capacitor 50 is set similarly as in Embodiment
1.
As described above, in this embodiment, depending on the line
capacity between the charging high-voltage transmission circuit 800
and the developing high-voltage transmission circuit 900, the
capacitor 50 for suppressing the interference of the developing AC
bias with the charging DC bias is provided in the charging
high-voltage transmission circuit 800. As a result, not only an
effect similar to the effect of Embodiment 1 can be obtained, but
also a degree of freedom of arrangement of the capacitor 50 can be
enhanced compared with Embodiment 1.
Other Embodiments
In the above, the present invention was described in accordance
with specific embodiments, but the present invention is not limited
to the above-described embodiments.
In the above-described embodiments, the image forming apparatus
employed the DC charging type. In the DC charging type, the image
defect due to the interference of the developing AC bias with the
charging DC bias becomes conspicuous, and therefore, it can be said
that the present invention is particularly effective. However, the
present invention is not limited thereto. Also in the AC charging
type, interference of the developing AC bias with the charging DC
bias (DC component) or the like can be suppressed.
In the above-described embodiments, the case where the charging
member contacts the surface of the photosensitive drum which is a
member to be electrically charged was described as an example, but
the charging member is not necessarily required to contact the
surface of the photosensitive drum. When an electrically
dischargeable region based on Paschen's law is provided between the
charging member and the photosensitive drum, the charging member
and the photosensitive drum may also be disposed without contact in
proximity with each other with a gap (spacing) of about several
tens of .mu.m.
Further, the charging member is not limited to the roller-shaped
member, but may also be an endless belt stretched by a plurality of
stretching rollers or a blade-like member, for example. Further,
the image bearing member is not limited to the drum-shaped
photosensitive member (photosensitive drum), but may also be an
endless belt-shaped photosensitive member (photosensitive belt),
for example. Further, when an image forming apparatus of an
electrostatic recording type is used, the image bearing member may
also be an electrostatic recording dielectric member formed in a
drum shape or an endless belt shape.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2017-100178 filed on May 19, 2017, which is hereby incorporated
by reference herein in its entirety.
* * * * *